In-depth study of PHP function checking methods available

We are using

PHP check function availability 1. Get all available modules-get_loaded_extensions
This function returns all loaded (available) modules.

Usage:

Print_r (get_loaded_extensions ());

PHP check function available 2. Get the available function of the specified module-get_extension_funcs
This function returns all available functions of the specified module. The input parameter (Module name) must be in lowercase.

Usage:

Print_r (get_extension_funcs ("gd "));

PHP check function available 3. Get all defined functions-get_defined_functions
This function returns all defined functions, including built-in functions and user-defined functions.

Usage:

 
 

  
  
function myrow($id, $data){   
  
  
return "<tr><th>$id</th><td>$data</td></tr>n";   
  
  
}   
  
  
$arr = get_defined_functions();   
  
  
print_r($arr);   
 
 

Output:

 
 

  
  
Array   
  
  
(   
  
  
[internal] => Array   
  
  
(   
  
  
[0] => zend_version   
  
  
[1] => func_num_args   
  
  
[2] => func_get_arg   
  
  
[3] => func_get_args   
  
  
[4] => strlen   
  
  
[5] => strcmp   
  
  
[6] => strncmp   
  
  
...   
  
  
[750] => bcscale   
  
  
[751] => bccomp   
  
  
)   
  
  
[user] => Array   
  
  
(   
  
  
[0] => myrow   
  
  
)   
  
  
)  
 
 

$ Arr ["internal"] is a built-in function, and $ arr ["user"] is a user-defined function.

PHP check function availability 4. Check whether the specified function exists-function_exists

This function returns whether the specified function has been defined.

Usage:

 
 

  
  
if (function_exists('imap_open')) {   
  
  
echo "IMAP functions are available.<br />n";   
  
  
} else {   
  
  
echo "IMAP functions are not available.<br />n";