<?php
$test = "dasdas, asdasd, 10 the high st, as dsad, asd as, asd asd,sdsad";
$pattern = '/^[^0-9]+([0-9]{1}).+$/';
preg_match( $pattern, $test, $matches, PREG_OFFSET_CAPTURE );
echo "First digit at position " . $matches[1][1];
?>
Outputs
First digit at position 16
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