3v4l.org

run code in 300+ PHP versions simultaneously
<?php $arr = array(1, 2, 3, 4, 4, 1, 2, 5, 5, 11, 11); // build and initialize array to track counts $count = array_flip( array_unique( $arr ) ); foreach( $count as $key => $value ) { $count[$key] = 0; } // counting ... foreach ($arr as $key => $value) { $count[$value] += 1; } // result: foreach ( $count as $item => $num ) { if ( $num == 1 ) { echo "$item appears only once.\n"; } }
Output for 4.3.0 - 4.3.11, 4.4.0 - 4.4.9, 5.0.0 - 5.0.5, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.30, 7.0.0 - 7.0.23, 7.1.0 - 7.1.25, 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
3 appears only once.
preferences:
157.96 ms | 410 KiB | 5 Q