PHP eval() function in PHP is an inbuilt function that evaluates a string as PHP code.
Syntax:
eval( $string )
Parameters: This function accepts a single parameter as shown in the above syntax and described below.
- $string: It must consist of a valid PHP code to be evaluated but should not contain opening and closing PHP tags.
Note: All statements must be properly terminated using a semicolon. For example, initializing the string as ‘echo “Geeks for Geeks”‘ will cause a parse error. To rectify, need to initialize as ‘echo “Geeks for Geeks”;’.
Return Value: Returns NULL unless a return statement is called in the input string containing PHP code. Then the value is returned. In case of a parse error in the input string, the function returns FALSE.
Examples:
Input : $age = 20; $str = "I am $age years old"
eval("\$str = \"$str\";");
Output : I am 20 years old
Input : $str = 'echo "Geeks for Geeks";';
echo eval($str). "\n";
Output : Geeks for Geeks
Below programs illustrate the use of eval() function:
Program 1:
php
<?php$age = 20;$str = 'My age is $age';echo $str. "\n";eval("\$str = \"$str\";");echo $str. "\n";?> |
My age is $age My age is 20
Program 2:
php
<?php$str = 'echo "Geeks for Geeks";';echo eval($str). "\n";?> |
Geeks for Geeks
Reference: http://php.net/manual/en/function.eval.php
