PHP: eval function - Evaluate a string as PHP code

Description

mixed eval ( string $code_str )

Evaluates the string given in code_str as PHP code. Among other things, this can be useful for storing code in a database text field for later execution.

There are some factors to keep in mind when using eval(). Remember that the string passed must be valid PHP code, including things like terminating statements with a semicolon so the parser doesn't die on the line after the eval(), and properly escaping things in code_str . To mix HTML output and PHP code you can use a closing PHP tag to leave PHP mode.

Also remember that variables given values under eval() will retain these values in the main script afterwards.

Parameters

code_str

The code string to be evaluated. code_str does not have to contain PHP Opening tags.

A return statement will immediately terminate the evaluation of the string .

Return Values

eval() returns NULL unless return is called in the evaluated code, in which case the value passed to return is returned. If there is a parse error in the evaluated code, eval() returns FALSE and execution of the following code continues normally. It is not possible to catch a parse error in eval() using set_error_handler().

Examples

Example #1 eval() example - simple text merge


<?php
$string = 'cup';
$name = 'coffee';
$str = 'This is a $string with my $name in it.';
echo $str. "\n";
eval("\$str = \"$str\";");
echo $str. "\n";
?>

The above example will output:

This is a $string with my $name in it.
This is a cup with my coffee in it.

Notes

Note: Because this is a language construct and not a function, it cannot be called using variable functions

Tip

As with anything that outputs its result directly to the browser, the output-control functions can be used to capture the output of this function, and save it in a string (for example).

Note: In case of a fatal error in the evaluated code, the whole script exits.