PHP函数，用于删除子字符串之前的所有内容（带有包含选项）

Question

I need help making a php function. I want to create a function that removes everything before a specific word or character in a string. I know how to do that part, but I am new to making a function out of it, and I need to add an option to it... for example. If I have this string...

$str="I like to eat cheese, crackers and ham";

And I want to remove everything before the word cheese I could use this...

if(($pos=strpos($str,'cheese'))!== false) $str=substr($str,$pos);

and I'd end up with

cheese, crackers and ham

if I want to include the word cheese in the removal, I could use...

if(($pos=strpos($str,'cheese'))!== false) $str=substr($str,$pos+6);

the +6 at the end is the length of the word "cheese". I would get...

, crackers and ham

I'd like to be able to use a function called remove_before to get my new string, like this...

$str=remove_before("cheese",$str,0);

The 3rd variable would indicate if you also want to remove the word you're looking for. A zero here would mean, remove everything before the word cheese and a 1 would mean remove the word cheese AND everything before it. Thank you.

Answer 1

What you're looking for is something like this:

<?php
function remove_before($needle, $haystack, $removeNeedle=false) {

    $pos = strpos($haystack, $needle);

    if (($pos !== false)) {
        return substr($haystack, $pos + (strlen($needle) * $removeNeedle));
    }

    return $haystack; // if word not found, return full string.
}

$needle = "cheese";
$haystack = "I like to eat cheese, crackers and ham";

echo remove_before($needle, $haystack, false);
?>

$pos + (strlen($needle)*$removeNeedle) $removeNeedle is a boolean, meaning its value is either 1 or 0. if you multiply by 1, then value is value, if you multiply by 0, value is 0. so basically, you multiply the length of needle by 1 or 0.

The boolean at the end, is optional, as its default value is false.

The code is written by me, and is free of use to anyone, without limit.

Answer 2

<?php
$str = "I like to eat cheese, crackers and ham";

function remove_before($needle, $haystack, $include = false)
{
    $pos = strpos($haystack, $needle);
    if ($pos !== false) {
        if (!$include) {
            $pos += strlen($needle);
        }
        return substr($haystack, $pos, strlen($haystack));
    }
    return null;
}

echo remove_before('cheese', $str, true);
echo remove_before('cheese', $str);

> cheese, crackers and ham
> , crackers and ham

Take a look at the documentation for creating functions http://php.net/manual/en/functions.user-defined.php

But also look at the documentation for passing arguments to functions http://php.net/manual/en/functions.arguments.php

What you want to pay attention to in the second link is passing default arguments. This allows for you to set a default value for an $arg that when it isn't set manually, defaults to the defined value. This allows for PHP to mock the function overloading of other languages.

Also it is important to do some sort of error checking inside of your function, depending on the defaults set, where my example just assumes that the user will pass a boolean value.

Answer 3

function remove_before ($needle, $haystack, $isNotIncluded) {
  if(($pos=strpos($haystack,$needle))!== false) 
    $haystack=substr($haystack,$isNotIncluded?$pos + strlen ($needle) :$pos);
  return $haystack;
}

//sorry, i'm typing on Galaxy s6, so I'm still not check it. Please try and double check substr, strlen... I just give you the basic function synstax.