GCM Notifications not receiving when app is in background mode in iOS

I have added

 'content_available' => true,//to trigger when iOS app is in background
 'priority' => 'high',
 'notification' => $data,
 $data = array( 'message' => 'Hello World!', 'body' => 'Hello World!');

to your code. Please try below code;

<?php

// Payload data you want to send to iOSdevice(s)
// (it will be accessible via intent extras)    
$data = array( 'message' => 'Hello World!', 'body' => 'Hello World!');

// The recipient registration tokens for this notification
// http://developer.android.com/google/gcm/ 
$ids = array( 'kucy6xoUmx********eeRsla' );

// Send a GCM push
sendGoogleCloudMessage(  $data, $ids );

function sendGoogleCloudMessage( $data, $ids )
{
    // Insert real GCM API key from Google APIs Console
    // https://code.google.com/apis/console/        
    $apiKey = 'AIz******9JA';

    // Define URL to GCM endpoint
    $url = 'https://gcm-http.googleapis.com/gcm/send';

    // Set GCM post variables (device IDs and push payload)     
    $post = array(
                    'registration_ids'  => $ids,
                    'data'              => $data, 
                    'content_available'    => true,                 
                    'priority'              => 'high',    
                    'notification' => $data,               
                    );

    // Set CURL request headers (authentication and type)       
    $headers = array( 
                        'Authorization: key=' . $apiKey,
                        'Content-Type: application/json'
                    );

    // Initialize curl handle       
    $ch = curl_init();

    // Set URL to GCM endpoint      
    curl_setopt( $ch, CURLOPT_URL, $url );

    // Set request method to POST       
    curl_setopt( $ch, CURLOPT_POST, true );

    // Set our custom headers       
    curl_setopt( $ch, CURLOPT_HTTPHEADER, $headers );

    // Get the response back as string instead of printing it       
    curl_setopt( $ch, CURLOPT_RETURNTRANSFER, true );

    // Set JSON post data
    curl_setopt( $ch, CURLOPT_POSTFIELDS, json_encode( $post ) );

    // Actually send the push   
    $result = curl_exec( $ch );

    // Error handling
    if ( curl_errno( $ch ) )
    {
        echo 'GCM error: ' . curl_error( $ch );
    }

    // Close curl handle
    curl_close( $ch );

    // Debug GCM response       
    echo $result;
}

?>

on IOS side; Follow orders on GCM Site

EDIT 1: You may try sending notification for ios;

I edited your php code above; Changes are;

'notification' => $data,

and

$data = array( 'message' => 'Hello World!', 'body' => 'Hello World!');

GCM receiving notification in invalid state 2.

Developers who are using GCM integration for both Android and iOS need to add specific things in their Post call to the GCM Server. For iOS: We need two additional things to make the same call work in iOS: 'notification' => $data, 'content_available'=> 'true',

The Apple push notifications service requires content_available is true. And then 'notification'=> $data helps the Notification center to know that the notification has arrived and needs to be pushed to the device.