php function eval () Introduction and use Example _php instance

What is eval ()?

The eval () function calculates the string according to the PHP code.
The string must be a valid PHP code and must end with a semicolon.
Returns NULL if the return statement is not invoked in the code string. If there is a parse error in the code, the eval () function returns FALSE.

Grammar

Eval (Phpcode)

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Parameter description
Phpcode required. Specify the PHP code to be computed.

Example 1

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<?php
$string = "Beautiful";
$time = "Winter";

$str = ' is a $string $time morning! ';
echo $str. "<br/>";

Eval ("\ $str = \" $str \ ";");
Echo $str;
?>

Output:
This is a $string $time morning!
This is a beautiful winter morning!

Example 2

We use the For loop to create n random, and the values multiply

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<?php

For ($i =1 $i <=10; $i + +) {
Eval (' $a '. $i. ' = '. $i * $i).
}

For ($i =1 $i <=10; $i + +) {
Eval (' echo $a '. $i. ' <br/>\ '; ');
}

echo ' <br/> ';
Echo $a 1 + $a 10;

Output:

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1
4
9
16
25
36
49
64
81
100
101