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php requires a dilimiter then exploding if you have a long.string you will need to extract the data portion before exploding the string into an array
$txt = 'A long string 1,2,3,4,5';
explode(',', $txt);
outputs an array like this: ['A long string 1', '2', '3', '4', '5']
You can use functions like substr to extract the string protion you need before you use explode to remove unwanted text.