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run code in 300+ PHP versions simultaneously
<?php $array = [ 'FILE-F01-E1-S01.pdf', 'FILE-F01-E1-S02.pdf', 'FILE-F01-E1-S03.pdf', 'FILE-F01-E1-S04.pdf', 'FILE-F01-E1-S05.pdf', 'FILE-F02-E1-S01.pdf', 'FILE-F02-E1-S02.pdf', 'FILE-F02-E1-S03.pdf', "TESTFILE-F01-E1-S03.pdf" ]; $parts = explode('-', $array[0]); array_pop($parts); $fileBeginning = implode('-', $parts); $secondArray = array_filter($array, function ($x) use ($fileBeginning) { return substr($x, 0, strlen($fileBeginning)) === $fileBeginning; }); print_r($secondArray);
Output for 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.26, 8.4.1 - 8.4.13
Array ( [0] => FILE-F01-E1-S01.pdf [1] => FILE-F01-E1-S02.pdf [2] => FILE-F01-E1-S03.pdf [3] => FILE-F01-E1-S04.pdf [4] => FILE-F01-E1-S05.pdf )

preferences:
138.25 ms | 408 KiB | 5 Q