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<?php $values = array('a'=>'foo','b'=>null,'c'=>'bar','d'=>''); foreach ($values as $field=>&$value) { if ($value === null || $value == '') { echo "$field is NULL,"; $value = null; continue; } $value = 'OK:'.$value; } var_dump($values); ?>
Output for 5.2.1 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.38, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6
b is NULL,d is NULL,array(4) { ["a"]=> string(6) "OK:foo" ["b"]=> NULL ["c"]=> string(6) "OK:bar" ["d"]=> &NULL }
Output for 5.0.0 - 5.0.5, 5.1.0 - 5.1.6, 5.2.0
b is NULL,d is NULL,array(4) { ["a"]=> &string(6) "OK:foo" ["b"]=> &NULL ["c"]=> &string(6) "OK:bar" ["d"]=> &NULL }
Output for 4.4.2 - 4.4.9
Parse error: syntax error, unexpected '&', expecting T_VARIABLE or '$' in /in/TF5DN on line 3
Process exited with code 255.
Output for 4.3.0 - 4.3.1, 4.3.5 - 4.3.11, 4.4.0 - 4.4.1
Parse error: parse error, unexpected '&', expecting T_VARIABLE or '$' in /in/TF5DN on line 3
Process exited with code 255.
Output for 4.3.2 - 4.3.4
Parse error: parse error, expecting `T_VARIABLE' or `'$'' in /in/TF5DN on line 3
Process exited with code 255.

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