Editing Eval (section)

=== PHP ===
In [[PHP]], <code>eval</code> executes code in a string almost exactly as if it had been put in the file instead of the call to <code>eval()</code>. The only exception is that errors are reported as coming from a call to <code>eval()</code>, and return statements become the result of the function.

Unlike some languages, the argument to <code>eval</code> must be a string of one or more complete statements, not just expressions; however, one can get the "expression" form of <code>eval</code> by putting the expression in a return statement, which causes <code>eval</code> to return the result of that expression.

Unlike some languages, PHP's <code>eval</code> is a "language construct" rather than a function,<ref>{{cite web|url=https://php.net/eval|website=[[PHP]].net|access-date=September 10, 2015|title=PHP: eval - Manual}}</ref> and so cannot be used in some contexts where functions can be, like higher-order functions.

Example using echo:
<syntaxhighlight lang="php">
<?php
$foo = "Hello, world!\n";
eval('echo "$foo";');
?>
</syntaxhighlight>

Example returning a value:
<syntaxhighlight lang="php">
<?php
$foo = "Goodbye, world!\n";  //does not work in PHP5
echo eval('return $foo;');
?>
</syntaxhighlight>