php获取数组中特定索引的值

I have this problem. I want to echo the value of the specific index of an array. my code is this.

<?php
$str = 'test1:val1,test2:val2,test3:val3'
$ex1 = explode(',',$str);
foreach($ex1 as $val){
  $ex2 = explode(':',$val);
  foreach($ex2 as $val2){
    echo $val2.'<br>';
  }
}

//the output will be
/*
test1
val1
test2
val2
test3
val3
*/
?>

But I want the output to be only test1,test2,test3. Plss someone help me.

</div>

Just get the substring with substr & strpos. Try with -

$str = 'test1:val1,test2:val2,test3:val3';
$ex1 = explode(',',$str);

foreach($ex1 as $val){
  $test = substr($val, 0, strpos($val, ':'));
  echo $test."<br>";
}

Or you can do this also -

$str = 'test1:val1,test2:val2,test3:val3';
$ex1 = explode(',',$str);
foreach($ex1 as $val){
  $ex2 = explode(':',$val);
  echo $ex2[0]."<br>";
}

You've already accepted an answer, but you can skip a couple lines and do a preg_match_all():

$str = 'test1:val1,test2:val2,test3:val3';
preg_match_all('/([^\,\:]{1,})\:([^\,\:]{1,})/',$str,$match);
echo implode(",<br />",$match[1]);