array -> base64_encode

array_to_base64_encode.php

<?php

/**
 * @param array $a
 * @return string
 */
function array_to_base64_encode( array $a ) {
  $table = preg_split('//', 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/', -1, PREG_SPLIT_NO_EMPTY);
  $l = count($a);
  $m = $l % 3;
  $buf = array();
  for( $i=0; $i<=$l-3; $i+=3 ) {
    $j = ($a[$i] << 16) | ($a[$i+1] << 8) | $a[$i+2];
    array_push( $buf, $table[$j >> 18 & 63], $table[$j >> 12 & 63], $table[$j >>  6 & 63], $table[$j & 63] );
  }
  if ( $m === 1) {
    $j = $a[$i] << 16;
    array_push( $buf, $table[$j >> 18 & 63], $table[$j >> 12 & 63], '==' );
  } else if( $m === 2 ) {
    $j = ( $a[$i] << 16) | ($a[$i + 1] << 8);
    array_push( $buf, $table[$j >> 18 & 63], $table[$j >> 12 & 63], $table[$j >>  6 & 63], '=' );
  }
  return implode( "", $buf );
}

var_dump( array_to_base64_encode( array(1,2,3,4) ) ); // string(8) "AQIDBA=="