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<?php $attendance = array( array( "student_id" => "1", "date" => "2016-04-24" ) ); $students = array( array( "student_id" => "1", "Reason" => "", "date" => "2016-04-24" ), array( "student_id" => "6", "Reason" => "1", "date" => "2016-04-24" ) ); $atts = array(); foreach($attendance as $att) { $atts[] = $att['student_id']; } foreach($students as &$student) { if(in_array($student['student_id'], $atts)) { $student['Reason']='1'; } else { $student['Reason']='0'; } } echo '<pre>',print_r($students,1),'</pre>';
Output for 5.5.0 - 5.5.35, 5.6.0 - 5.6.28, 7.0.0 - 7.0.20, 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 - 8.1.29, 8.2.0 - 8.2.21, 8.3.0 - 8.3.9
<pre>Array ( [0] => Array ( [student_id] => 1 [Reason] => 1 [date] => 2016-04-24 ) [1] => Array ( [student_id] => 6 [Reason] => 0 [date] => 2016-04-24 ) ) </pre>

preferences:
195.85 ms | 405 KiB | 235 Q