<?php
 
$url = 'https://hostname:2003/index.php?api=json&act=multi_php&apiuser=user_name&apikey=pass_api_key'; 

$post = array('submitphp' => 'apply',
	      'domain.com' => 'domain.com',
	      'php_version_domain.com' => 'php_version(php72)'
);


// Set the curl parameters 
$ch = curl_init(); 
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, FALSE);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 5); 
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); 

if(!empty($post)){
	curl_setopt($ch, CURLOPT_POST, 1);
	curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($post));
}

// Get response from the server. 
$resp = curl_exec($ch);

// The response will hold a string as per the API response method. 
$res = json_decode($resp, true);
// Done ?
if(!empty($res['done'])){
    echo "<pre>";
    print_r($res['done']['msg']);
    echo "</pre>";
}else{
	print_r($res['error']);
}