(PHP 4 >= 4.2.0, PHP 5, PHP 7)
apache_setenv — Set an Apache subprocess_env variable
$variable
   , string $value
   [, bool $walk_to_top = false
  ] )
   apache_setenv() sets the value of the Apache
   environment variable specified by
   variable.
  
Note:
When setting an Apache environment variable, the corresponding $_SERVER variable is not changed.
variableThe environment variable that's being set.
value
       The new variable value.
      
walk_to_topWhether to set the top-level variable available to all Apache layers.
   Returns TRUE on success or FALSE on failure.
  
Example #1 Setting an Apache environment variable using apache_setenv()
<?php
apache_setenv("EXAMPLE_VAR", "Example Value");
?>
Note:
apache_setenv() can be paired up with apache_getenv() across separate pages or for setting variables to pass to Server Side Includes (.shtml) that have been included in PHP scripts.