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<title>Checks if assertion is FALSE</title>
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</div><hr /><div id="function.assert" class="refentry">
<div class="refnamediv">
<h1 class="refname">assert</h1>
<p class="verinfo">(PHP 4, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">assert</span> — <span class="dc-title">Checks if assertion is <strong><code>FALSE</code></strong></span></p>
</div>
<div class="refsect1 description" id="refsect1-function.assert-description">
<h3 class="title">Description</h3>
<p class="para">PHP 5 and 7</p>
<div class="methodsynopsis dc-description">
<span class="type">bool</span> <span class="methodname"><strong>assert</strong></span>
( <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$assertion</code></span>
[, <span class="methodparam"><span class="type">string</span> <code class="parameter">$description</code></span>
] )</div>
<p class="para rdfs-comment">PHP 7</p>
<div class="methodsynopsis dc-description">
<span class="type">bool</span> <span class="methodname"><strong>assert</strong></span>
( <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$assertion</code></span>
[, <span class="methodparam"><span class="type"><a href="class.throwable.html" class="type Throwable">Throwable</a></span> <code class="parameter">$exception</code></span>
] )</div>
<p class="para rdfs-comment">
<span class="function"><strong>assert()</strong></span> will check the given
<code class="parameter">assertion</code> and take appropriate action if
its result is <strong><code>FALSE</code></strong>.
</p>
<div class="refsect2 unknown-descriptioo" id="refsect2-function.assert-unknown-descriptioo">
<h4 class="title">Traditional assertions (PHP 5 and 7)</h4>
<p class="para">
If the <code class="parameter">assertion</code> is given as a string it
will be evaluated as PHP code by <span class="function"><strong>assert()</strong></span>.
If you pass a boolean condition as <code class="parameter">assertion</code>,
this condition will not show up as parameter to the assertion function
which you may have defined with <span class="function"><a href="function.assert-options.html" class="function">assert_options()</a></span>.
The condition is converted to a string before calling that handler
function, and the boolean <strong><code>FALSE</code></strong> is converted as the empty string.
</p>
<p class="para">
Assertions should be used as a debugging feature only. You may
use them for sanity-checks that test for conditions that should
always be <strong><code>TRUE</code></strong> and that indicate some programming errors if not
or to check for the presence of certain features like extension
functions or certain system limits and features.
</p>
<p class="para">
Assertions should not be used for normal runtime operations like
input parameter checks. As a rule of thumb your code should
always be able to work correctly if assertion checking is not
activated.
</p>
<p class="para">
The behavior of <span class="function"><strong>assert()</strong></span> may be configured by
<span class="function"><a href="function.assert-options.html" class="function">assert_options()</a></span> or by .ini-settings described
in that functions manual page.
</p>
<p class="para">
The <span class="function"><a href="function.assert-options.html" class="function">assert_options()</a></span> function and/or
<strong><code>ASSERT_CALLBACK</code></strong> configuration directive allow a
callback function to be set to handle failed assertions.
</p>
<p class="para">
<span class="function"><strong>assert()</strong></span> callbacks are particularly useful for
building automated test suites because they allow you to easily
capture the code passed to the assertion, along with information
on where the assertion was made. While this information can be
captured via other methods, using assertions makes it much faster
and easier!
</p>
<p class="para">
The callback function should accept three arguments. The first
argument will contain the file the assertion failed in. The
second argument will contain the line the assertion failed on and
the third argument will contain the expression that failed (if
any — literal values such as 1 or "two" will not be passed via
this argument). Users of PHP 5.4.8 and later may also provide a fourth
optional argument, which will contain the
<code class="parameter">description</code> given to <span class="function"><strong>assert()</strong></span>, if
it was set.
</p>
</div>
<div class="refsect2 unknown-unknown-descriptiop" id="function.assert.expectations">
<h4 class="title">Expectations (PHP 7 only)</h4>
<p class="para">
<span class="function"><strong>assert()</strong></span> is a language construct in PHP 7, allowing for
the definition of expectations: assertions that take effect in development
and testing environments, but are optimised away to have zero cost in
production.
</p>
<p class="para">
While <span class="function"><a href="function.assert-options.html" class="function">assert_options()</a></span> can still be used to control
behaviour as described above for backward compatibility reasons, PHP 7
only code should use the two new configuration directives to control
the behaviour of <span class="function"><strong>assert()</strong></span> and not call
<span class="function"><a href="function.assert-options.html" class="function">assert_options()</a></span>.
</p>
<table class="doctable table">
<caption><strong>
PHP 7 configuration directives for <span class="function"><strong>assert()</strong></span>
</strong></caption>
<thead>
<tr>
<th>Directive</th>
<th>Default value</th>
<th>Possible values</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td>
<a href="ini.core.html#ini.zend.assertions" class="link">zend.assertions</a>
</td>
<td><em>1</em></td>
<td>
<ul class="simplelist">
<li class="member">
<em>1</em>: generate and execute code (development mode)
</li>
<li class="member">
<em>0</em>: generate code but jump around it at runtime
</li>
<li class="member">
<em>-1</em>: do not generate code (production mode)
</li>
</ul>
</td>
</tr>
<tr>
<td>
<a href="info.configuration.html#ini.assert.exception" class="link">assert.exception</a>
</td>
<td><em>0</em></td>
<td>
<ul class="simplelist">
<li class="member">
<em>1</em>: throw when the assertion fails, either by
throwing the object provided as the <code class="parameter">exception</code>
or by throwing a new <a href="class.assertionerror.html" class="classname">AssertionError</a> object if
<code class="parameter">exception</code> wasn't provided
</li>
<li class="member">
<em>0</em>: use or generate a
<a href="class.throwable.html" class="classname">Throwable</a> as described above, but only
generate a warning based on that object rather than throwing it
(compatible with PHP 5 behaviour)
</li>
</ul>
</td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="refsect1 parameters" id="refsect1-function.assert-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<code class="parameter">assertion</code></dt>
<dd>
<p class="para">
The assertion. In PHP 5, this must be either a <span class="type"><a href="language.types.string.html" class="type string">string</a></span> to
be evaluated or a <span class="type"><a href="language.types.boolean.html" class="type boolean">boolean</a></span> to be tested. In PHP 7, this may
also be any expression that returns a value, which will be executed and
the result used to indicate whether the assertion succeeded or failed.
</p>
<div class="warning"><strong class="warning">Warning</strong>
<p class="para">
Using <span class="type"><a href="language.types.string.html" class="type string">string</a></span> as the <code class="parameter">assertion</code> is
<em class="emphasis">DEPRECATED</em> as of PHP 7.2.
</p>
</div>
</dd>
<dt>
<code class="parameter">description</code></dt>
<dd>
<p class="para">
An optional description that will be included in the failure message if
the <code class="parameter">assertion</code> fails.
</p>
</dd>
<dt>
<code class="parameter">exception</code></dt>
<dd>
<p class="para">
In PHP 7, the second parameter can be a
<a href="class.throwable.html" class="classname">Throwable</a> object instead of a descriptive
<span class="type"><a href="language.types.string.html" class="type string">string</a></span>, in which case this is the object that will be
thrown if the assertion fails and the
<a href="info.configuration.html#ini.assert.exception" class="link">assert.exception</a>
configuration directive is enabled.
</p>
</dd>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.assert-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
<strong><code>FALSE</code></strong> if the assertion is false, <strong><code>TRUE</code></strong> otherwise.
</p>
</div>
<div class="refsect1 changelog" id="refsect1-function.assert-changelog">
<h3 class="title">Changelog</h3>
<p class="para">
<table class="doctable informaltable">
<thead>
<tr>
<th>Version</th>
<th>Description</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td>7.2.0</td>
<td>
Usage of a <span class="type"><a href="language.types.string.html" class="type string">string</a></span> as the <code class="parameter">assertion</code>
became deprecated. It now emits an <strong><code>E_DEPRECATED</code></strong>
notice when both <a href="info.configuration.html#ini.assert.active" class="link">assert.active</a>
and <a href="ini.core.html#ini.zend.assertions" class="link">zend.assertions</a> are set
to <em>1</em>.
</td>
</tr>
<tr>
<td>7.0.0</td>
<td>
<span class="function"><strong>assert()</strong></span> is now a language construct and not a
function. <code class="parameter">assertion</code> can now be an expression.
The second parameter is now interpreted either as an
<code class="parameter">exception</code> (if a
<a href="class.throwable.html" class="classname">Throwable</a> object is given), or as the
<code class="parameter">description</code> supported from PHP 5.4.8 onwards.
</td>
</tr>
<tr>
<td>5.4.8</td>
<td>
The <code class="parameter">description</code> parameter was added. The
<code class="parameter">description</code> is also now provided to a callback
function in <strong><code>ASSERT_CALLBACK</code></strong> mode as the fourth
argument.
</td>
</tr>
</tbody>
</table>
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.assert-examples">
<h3 class="title">Examples</h3>
<div class="refsect2 unknown-examplet" id="refsect2-function.assert-unknown-examplet">
<h4 class="title">Traditional assertions (PHP 5 and 7)</h4>
<p class="para">
<div class="example" id="example-520">
<p><strong>Example #1 Handle a failed assertion with a custom handler</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// Active assert and make it quiet<br /></span><span style="color: #0000BB">assert_options</span><span style="color: #007700">(</span><span style="color: #0000BB">ASSERT_ACTIVE</span><span style="color: #007700">, </span><span style="color: #0000BB">1</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">assert_options</span><span style="color: #007700">(</span><span style="color: #0000BB">ASSERT_WARNING</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">assert_options</span><span style="color: #007700">(</span><span style="color: #0000BB">ASSERT_QUIET_EVAL</span><span style="color: #007700">, </span><span style="color: #0000BB">1</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// Create a handler function<br /></span><span style="color: #007700">function </span><span style="color: #0000BB">my_assert_handler</span><span style="color: #007700">(</span><span style="color: #0000BB">$file</span><span style="color: #007700">, </span><span style="color: #0000BB">$line</span><span style="color: #007700">, </span><span style="color: #0000BB">$code</span><span style="color: #007700">)<br />{<br /> echo </span><span style="color: #DD0000">"<hr>Assertion Failed:<br /> File '</span><span style="color: #0000BB">$file</span><span style="color: #DD0000">'<br /><br /> Line '</span><span style="color: #0000BB">$line</span><span style="color: #DD0000">'<br /><br /> Code '</span><span style="color: #0000BB">$code</span><span style="color: #DD0000">'<br /><hr />"</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #FF8000">// Set up the callback<br /></span><span style="color: #0000BB">assert_options</span><span style="color: #007700">(</span><span style="color: #0000BB">ASSERT_CALLBACK</span><span style="color: #007700">, </span><span style="color: #DD0000">'my_assert_handler'</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// Make an assertion that should fail<br /></span><span style="color: #0000BB">assert</span><span style="color: #007700">(</span><span style="color: #DD0000">'mysql_query("")'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
<p class="para">
<div class="example" id="example-521">
<p><strong>Example #2 Using a custom handler to print a description</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// Active assert and make it quiet<br /></span><span style="color: #0000BB">assert_options</span><span style="color: #007700">(</span><span style="color: #0000BB">ASSERT_ACTIVE</span><span style="color: #007700">, </span><span style="color: #0000BB">1</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">assert_options</span><span style="color: #007700">(</span><span style="color: #0000BB">ASSERT_WARNING</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">assert_options</span><span style="color: #007700">(</span><span style="color: #0000BB">ASSERT_QUIET_EVAL</span><span style="color: #007700">, </span><span style="color: #0000BB">1</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// Create a handler function<br /></span><span style="color: #007700">function </span><span style="color: #0000BB">my_assert_handler</span><span style="color: #007700">(</span><span style="color: #0000BB">$file</span><span style="color: #007700">, </span><span style="color: #0000BB">$line</span><span style="color: #007700">, </span><span style="color: #0000BB">$code</span><span style="color: #007700">, </span><span style="color: #0000BB">$desc </span><span style="color: #007700">= </span><span style="color: #0000BB">null</span><span style="color: #007700">)<br />{<br /> echo </span><span style="color: #DD0000">"Assertion failed at </span><span style="color: #0000BB">$file</span><span style="color: #DD0000">:</span><span style="color: #0000BB">$line</span><span style="color: #DD0000">: </span><span style="color: #0000BB">$code</span><span style="color: #DD0000">"</span><span style="color: #007700">;<br /> if (</span><span style="color: #0000BB">$desc</span><span style="color: #007700">) {<br /> echo </span><span style="color: #DD0000">": </span><span style="color: #0000BB">$desc</span><span style="color: #DD0000">"</span><span style="color: #007700">;<br /> }<br /> echo </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #FF8000">// Set up the callback<br /></span><span style="color: #0000BB">assert_options</span><span style="color: #007700">(</span><span style="color: #0000BB">ASSERT_CALLBACK</span><span style="color: #007700">, </span><span style="color: #DD0000">'my_assert_handler'</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// Make an assertion that should fail<br /></span><span style="color: #0000BB">assert</span><span style="color: #007700">(</span><span style="color: #DD0000">'2 < 1'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">assert</span><span style="color: #007700">(</span><span style="color: #DD0000">'2 < 1'</span><span style="color: #007700">, </span><span style="color: #DD0000">'Two is less than one'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
Assertion failed at test.php:21: 2 < 1
Assertion failed at test.php:22: 2 < 1: Two is less than one
</pre></div>
</div>
</div>
</p>
</div>
<div class="refsect2 unknown-unknown-exampleu" id="refsect2-function.assert-unknown-unknown-exampleu">
<h4 class="title">Expectations (PHP 7 only)</h4>
<div class="example" id="example-522">
<p><strong>Example #3 Expectations without a custom exception</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />assert</span><span style="color: #007700">(</span><span style="color: #0000BB">true </span><span style="color: #007700">== </span><span style="color: #0000BB">false</span><span style="color: #007700">);<br />echo </span><span style="color: #DD0000">'Hi!'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>
With <a href="ini.core.html#ini.zend.assertions" class="link">zend.assertions</a> set to 0,
the above example will output:
</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
Hi!
</pre></div>
</div>
<div class="example-contents"><p>
With <a href="ini.core.html#ini.zend.assertions" class="link">zend.assertions</a> set to 1
and <a href="info.configuration.html#ini.assert.exception" class="link">assert.exception</a> set to 0,
the above example will output:
</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
Warning: assert(): assert(true == false) failed in - on line 2
Hi!
</pre></div>
</div>
<div class="example-contents"><p>
With <a href="ini.core.html#ini.zend.assertions" class="link">zend.assertions</a> set to 1
and <a href="info.configuration.html#ini.assert.exception" class="link">assert.exception</a> set to 1,
the above example will output:
</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
Fatal error: Uncaught AssertionError: assert(true == false) in -:2
Stack trace:
#0 -(2): assert(false, 'assert(true == ...')
#1 {main}
thrown in - on line 2
</pre></div>
</div>
</div>
<div class="example" id="example-523">
<p><strong>Example #4 Expectations with a custom exception</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">class </span><span style="color: #0000BB">CustomError </span><span style="color: #007700">extends </span><span style="color: #0000BB">AssertionError </span><span style="color: #007700">{}<br /><br /></span><span style="color: #0000BB">assert</span><span style="color: #007700">(</span><span style="color: #0000BB">true </span><span style="color: #007700">== </span><span style="color: #0000BB">false</span><span style="color: #007700">, new </span><span style="color: #0000BB">CustomError</span><span style="color: #007700">(</span><span style="color: #DD0000">'True is not false!'</span><span style="color: #007700">));<br />echo </span><span style="color: #DD0000">'Hi!'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>
With <a href="ini.core.html#ini.zend.assertions" class="link">zend.assertions</a> set to 0,
the above example will output:
</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
Hi!
</pre></div>
</div>
<div class="example-contents"><p>
With <a href="ini.core.html#ini.zend.assertions" class="link">zend.assertions</a> set to 1
and <a href="info.configuration.html#ini.assert.exception" class="link">assert.exception</a> set to 0,
the above example will output:
</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
Warning: assert(): CustomError: True is not false! in -:4
Stack trace:
#0 {main} failed in - on line 4
Hi!
</pre></div>
</div>
<div class="example-contents"><p>
With <a href="ini.core.html#ini.zend.assertions" class="link">zend.assertions</a> set to 1
and <a href="info.configuration.html#ini.assert.exception" class="link">assert.exception</a> set to 1,
the above example will output:
</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
Fatal error: Uncaught CustomError: True is not false! in -:4
Stack trace:
#0 {main}
thrown in - on line 4
</pre></div>
</div>
</div>
</div>
</div>
<div class="refsect1 seealso" id="refsect1-function.assert-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"><span class="function"><a href="function.assert-options.html" class="function" rel="rdfs-seeAlso">assert_options()</a> - Set/get the various assert flags</span></li>
</ul>
</p>
</div>
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