It is basically the process  of catching the error that occurred in the program and then taking an appropriate action.

It is very simple to handle the error in php.

While writing the program we should check all the possible error condition before the executing.

ex

<?php
   if(!file_exists("/tmp/test.txt")) {
      die("File not found");
   }else {
      $file = fopen("/tmp/test.txt","r");
      print "Opend file sucessfully";
   }
   // Test of the code here.
?>

This is the way to find the error and display a message whenever error occur.

We can write our own error catching function

error_function(error_level,error_message, error_file,error_line,error_context);

This is the way to create an error handling program

<?php
   function handleError($errno, $errstr,$error_file,$error_line) {
      echo "<b>Error:</b> [$errno] $errstr - $error_file:$error_line";
      echo "<br />";
      echo "Terminating PHP Script";
      
      die();
   }
?>