The eval function in PHP is an inbuilt function that evaluates a string as PHP code.

1. Code:

<?php
 
$age = 20;
$str = 'My Soltuts $age years old';
echo $str. "<br>";
 
eval("\$str = \"$str\";");
echo $str. "<br>";
?>

2. Example:

Input:

Input : $age = 20; 
$str = "My Soltuts $age years old"
 eval("\$str = \"$str\";");

Output:

Output : My Soltuts 20 years old

3. Syntax:

Syntax: eval( $string )
Parameters: This function accepts a single parameter as shown in 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.