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Value of value in PHP

In PHP, general variables are declared using $. For example $abc, $xyz.

But in addition to that, PHP has a concept called value of value. The value of value is for storing the reference of another variable and that can be accomplished using the sign as $$ i.e. $$abc.

One simple example of storing value of value:

$$abc=”xyz”;
$xyz=5;

Now if you print $$abc and $xyz, both will print the value 5. See the following code

<?php
Echo $$abc; // this will display 5
Echo ${$abc} //another way of interpreting the same thing

Now, one may think that why we need value of value if I could store the value in a simple variable and the concept of ‘value of value’ is only increasing my effort. The reason of using this concept is late binding or says dynamic creation of variable name. See the following example.

<?php
$expected = array('name', 'email', 'comments');
$required = array('name', 'comments');
$missing = array();
foreach ($_POST as $key => $value) {
  // assign to temporary variable and strip whitespace if not an array
  $temp = is_array($value) ? $value : trim($value);
  // if empty and required, add to $missing array
  if (empty($temp) && in_array($key, $required)) {
    $missing[] = $key;
  } elseif (in_array($key, $expected)) {
    // otherwise, assign to a variable of the same name as $key
    ${$key} = $temp;
  }
}
?>

Posted By -	Geetanjali

Posted On -	Saturday, January 16, 2016

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