<?php
 
$date_day_pattern = '(?:0[1-9]|[12][0-9]|3[01])';
$date_month_pattern = '(?:0[1-9]|1[0-2])';
$date_year_pattern = '(?:[12][0-9]|20[12][0-9])';
$input = "dksj dkk\n49.. dk /ak 01-05-2012 hey\nkdks"; 
$prefix_pattern = '^(.*?)\s*';//(?<=[^\n]*)';
$date_pattern = "(?<!\d|\d )($date_day_pattern)[^\d\n]?($date_month_pattern)[^\d\n]?($date_year_pattern)(?!\d)";
echo "$date_pattern\n";
preg_match("/$prefix_pattern$date_pattern/m", $input, $matches);
print_r($matches);

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