Php 如何将0添加到循环的数组中的数字

每次当数字大于或等于2时，我都尝试添加

0

。例如：我不想要

a1，a10

，我想要

a01，a10

$a_l_demographics = [11,3,13];
$a_p_demographics  = ['a','b','c'];
$a_r_demographics = [];
$c_demographics_values = array();
$a_c_demographics = min(count($a_l_demographics), count($a_p_demographics));

for ($i = 0; $i < $a_c_demographics; $i++) {

  for ($j = 1; $j <= $a_l_demographics[$i]; $j++) {

    $a_r_demographics[] = $a_p_demographics[$i] . $j;

    // I tried to do something like this, but doesn't work.
    if (strlen(implode($a_r_demographics)) >= 2) {
      $a_r_demographics[] = '0'.$a_p_demographics[$i] . $j;
    } else {
      $a_r_demographics[] = $a_p_demographics[$i] . $j;
    }

    // or even this
    /*
    switch (true) {
      case $i <= 10:
        $a_r_demographics[] = '0'.$a_p_demographics[$i] . $j;
        break;
    }
    */

    echo implode($a_r_demographics);

  }

}

$a_l_人口统计=[11,3,13]；
$a_p_人口统计=['a'，'b'，'c']；
$a_r_人口统计=[]；
$c_demographics_values=array（）；
$a_c_demographics=min（计数（$a_l_demographics），计数（$a_p_demographics））；
对于（$i=0；$i<$a_c_人口统计；$i++）{
对于（$j=1；$j
当数字大于或等于2长度时，可能重复的
添加0
？所以您想将0添加到，例如，100？您应该尝试类似stru pad（）的方法。干得好。谢谢。
<?php
    $a_l_demographics = [11,3,13];
    $a_p_demographics  = ['a','b','c'];
    $a_r_demographics = [];
    $c_demographics_values = array();
    $a_c_demographics = min(count($a_l_demographics), count($a_p_demographics));

    for ($i = 0; $i < $a_c_demographics; $i++) {
        for ($j = 1; $j <= $a_l_demographics[$i]; $j++) {
            $a_r_demographics[] = $a_p_demographics[$i] . str_pad($j, 2, 0, STR_PAD_LEFT);
        }
    }
    echo implode($a_r_demographics, ',');