- str_replace: documentation ( source)
<?php
$cpc = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-_';
$std = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_';
$sql = '{}';
for ($i = 0; $i < 64; $i++) {
$sql = str_replace('{}', 'REPLACE({}, "'.$cpc[$i].'", "'.$std[$i].'")', $sql);
}
echo str_replace('{}', 'TRIM(TRAILING "=" FROM TO_BASE64(UNHEX(HEX(CEIL(UNIX_TIMESTAMP(conversionTs) * 1000000)))))', $sql);