SMS Length calculations, using GSM 03.38 and GSM 03.40

2.0.1 2022-06-26 04:31 UTC

This package is auto-updated.

Last update: 2024-07-01 00:08:15 UTC



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Calculate SMS GSM 03.38 message encoding and length, and number of concatenated SMS required


composer require phlib/sms-length


Simple string which fits within GSM 03.38 7-bit alphabet:

$smsLength = new \Phlib\SmsLength\SmsLength('simple message');
$smsLength->validate(); // Throw exceptions for any validation failures
$smsLength->getSize(); // 14
$smsLength->getEncoding(); // '7-bit'
$smsLength->getMessageCount(); // 1
$smsLength->getUpperBreakpoint(); // 160

Message which contains characters forcing switch to using GSM 03.38 UCS-2:

$smsLength = new \Phlib\SmsLength\SmsLength('message with • char requiring UCS-2');
$smsLength->validate(); // Throw exceptions for any validation failures
$smsLength->getSize(); // 35
$smsLength->getEncoding(); // 'ucs-2'
$smsLength->getMessageCount(); // 1
$smsLength->getUpperBreakpoint(); // 70


In the course of adding an SMS module to our Commercial software, we have found need for the SMS length properties which we've included in this package.

Our third-party SMS gateway provider's API will of course error if the message length exceeds the maximum allowed, and handles the correct concatenation and encoding for the given UTF-8 string.

However we want to be able to inform our users of message size and limits while they're building their SMS campaign (in advance of a live send). Plus we also need to show how many concatenated SMS they will use per contact, and therefore indicate pricing.

The unit tests and inspections made by this package are based on GSM 03.38 / 3GPP 23.038 for encoding and GSM 03.40 / 3GPP 23.040 for concatenated SMS. We have also referred to documentation provided by third-party SMS gateway providers such as MessageBird and Messente.


This package is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this program. If not, see