<?php
 
$a[0] =  'dbbackup_2014.09.03_07_06_27';
$a[1] =  'dbbackup_2014.09.03_07_07_08';
$a[2] =  'dbbackup_2014.09.03_07_13_33';
$a[3] =  'dbbackup_2014.09.03_07_15_24';
$a[4] =  'dbbackup_2014.09.03_07_21_57';
$a[5] =  'dbbackup_2014.09.03_07_22_11';
$a[6] =  'dbbackup_2014.09.03_08_40_35';
$a[7] =  'dbbackup_2014.09.03_08_41_36';
$a[8] =  'dbbackup_2014.09.03_08_43_38';
$a[9] =  'dbbackup_2014.09.04_04_59_08';
$a[10] =  'dbbackup_2014.09.03_07_06_27';
$a[11] =  'dbbackup_2014.09.03_07_07_08';
$a[12] =  'dbbackup_2014.09.03_07_13_33';
$a[13] =  'dbbackup_2014.09.03_07_15_24';
$a[14] =  'dbbackup_2014.09.03_07_21_57';
$a[15] =  'dbbackup_2014.09.03_07_22_11';
$a[16] =  'dbbackup_2014.09.03_08_40_35';
$a[17] =  'dbbackup_2014.09.03_08_41_36';
$a[18] =  'dbbackup_2014.09.03_08_43_38';
 
$a = array_flip(array_filter(array_count_values($a),function($item){
	return $item == 1 ? true : false;
}));
print_r($a);
 

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