Detailed explanation of in_array in php

<?php
$arr = array(
&#39;aaa&#39;, &#39;bbb&#39;,3
);
if( in_array(&#39;3月&#39;,$arr) ){
  echo &#39;11&#39;.PHP_EOL;
}else{
echo 22;
}
echo &#39;------------------------&#39;;  //输出11
$arr = array(
&#39;aaa&#39;, &#39;bbb&#39;,3
);
if( in_array(&#39;3月&#39;,$arr,true) ){
  echo &#39;11&#39;.PHP_EOL;
}else{
echo 22;
}
echo &#39;------------------------&#39;;//输出22
$arr = array(
&#39;aaa&#39;, &#39;bbb&#39;,&#39;3&#39;
);
if( in_array(&#39;3月&#39;,$arr) ){
  echo 11;
}else{
echo 22;
}  //输出22
?>