$re = '/<\?php echo \$(.*?)\[(.*?)\];\s*\?>/m';
$str = '<?php echo $rsedit[customer_name]; ?>
<?php echo $rsedit[address]; ?>
<?php echo $rsedit[city]; ?>
<?php echo $rsedit[pincode]; ?>
<?php echo $rsedit[contact_no]; ?>
<?php echo $rsedit[email_id]; ?>';
$subst = "<?php echo \$$1['$2']; ?>";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php