explode function creates an array of data from whichever bit of the data you wish you create it from...

explode("@", "a@b@c@d")[0]; Would Equals "a"
explode("@", "a@b@c@d")[1]; Would Equals "b"
explode("@", "a@b@c@d")[2]; Would Equals "c"

Counting In PHP always starts at "0", If "@" was the first charater in the explode string "0" would be null

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