PHP函数

1、strlen（）函数返回字符串长度

<?php
echo strlen("hello")
?>

 2、对字符串中的单词计数

<?php
echo str_word_count("do you know this");
?>

 3、反转字符串

<?php
echo strrev("do you know this");
?>

 4、替换字符串中文本

<?php
echo str_replace("this","that","do you know this");
?>

 5、对数组排序函数

sort() - 以升序对数组排序

rsort() - 以降序对数组排序

asort() - 根据值，以升序对关联数组进行排序

ksort() - 根据键，以升序对关联数组进行排序

arsort() - 根据值，以降序对关联数组进行排序

krsort() - 根据键，以降序对关联数组进行排序

例1：按字母升序/降序

<?php
$fruits=array("Banana","peach","apple");
sort($fruits);
$clength=count($fruits);
for($x=0;$x<$clength;$x++)
{
    echo $fruits[$x];
    echo "<br>";
}
?>

<?php
$fruits=array("Banana","peach","apple");
rsort($fruits);
$clength=count($fruits);
for($x=0;$x<$clength;$x++)
{
    echo $fruits[$x];
    echo "<br>";
}
?>

 例2：按数字升序/降序

<?php
$fruits=array(7,1,22,13);
sort($fruits);
$clength=count($fruits);
for($x=0;$x<$clength;$x++)
{
    echo $fruits[$x];
    echo "<br>";
}
?>

<?php
$fruits=array(7,1,22,13);
rsort($fruits);
$clength=count($fruits);
for($x=0;$x<$clength;$x++)
{
    echo $fruits[$x];
    echo "<br>";
}
?>

 例3：根据值对数组进行升序/降序

<?php
$age=array("ann"=>"30","tian"=>"18","bill"=>"26");
asort($age);

foreach($age as $x=>$x_value)
{
    echo "key=" . $x . ", value=" . $x_value;
    echo "<br>";
}
?>

<?php
$age=array("ann"=>"30","tian"=>"18","bill"=>"26");
arsort($age);

foreach($age as $x=>$x_value)
{
    echo "key=" . $x . ", value=" . $x_value;
    echo "<br>";
}
?>

 例4：根据键对数组进行升序/降序

<?php
$age=array("ann"=>"30","tian"=>"18","bill"=>"26");
ksort($age);

foreach($age as $x=>$x_value)
{
    echo "key=" . $x . ", value=" . $x_value;
    echo "<br>";
}
?>

<?php
$age=array("ann"=>"30","tian"=>"18","bill"=>"26");
krsort($age);

foreach($age as $x=>$x_value)
{
    echo "key=" . $x . ", value=" . $x_value;
    echo "<br>";
}
?>