Extraction of strings

There is a string:

$content="1+ssdsddss";

Please tell me how to use the php string function to extract "1+", thank you. (Beginners, please answer patiently, thank you)

Reply content:

There is a string:

$content="1+ssdsddss";

Please tell me how to use the php string function to extract "1+", thank you. (Beginners, please answer patiently, thank you)

$str = substr($content,2);