Analysis of the main steps of uploading images in PHP_PHP tutorial

When we are in actual operationThe principle of uploading pictures: first determine whether the file type is an image format, if so, upload the file, and then rename the file (usually to avoid uploading files with duplicate names, now Basically, they are named after the time), then upload the file to the specified directory, and output a preview of the uploaded image after successful upload.

PHP Upload Image 1. First we start to determine whether the file type is an image type.

{ strrchr: Find the last string in another string The position of an occurrence and returns all characters from that position to the end of the string. substr: Get part of the string. $HTTP_POST_FILES['file']['name']: Get the full name of the currently uploaded file. }

The picture type is the character after "." (for example: if a file name is XXX.JPG, then its type is JPG after "."). We can use functions in PHP to intercept the name of the uploader's file. Let's write a function to get the file type

function type() { return substr(strrchr($HTTP_POST_FILES['file']['name'],'.'),1); } ?>

PHP upload image 2. If so, upload the file, and then rename the function used in the file

{ strtolower: Convert all letters in the string to lowercase letters. in_array: Function searches for a given value in an array. implode: function combines array elements into a string random: randomly generated number $_FILES['userfile']['name']: upload file name $uploaddir: self-defined variable. For example, in the same folder, if you want to put the uploaded files into the FILE folder of this folder, you can define $uploaddir="./file/" like this; pay attention to the writing}

here Many problems will arise. First, write an array of uploadable types. Second, determine the legality of the document. Third, rename the file. *(I will not write it here to determine the file size) first define the type array that allows uploading files: $type=array("jpg", "gif", "bmp", "jpeg", "png"); second use an IF. . else. . Write a control flow statement to determine the legality of the file.

if(!in_arry(strtolower(type()),$type))//If there is no type that can be uploaded{ $text=implode('.',$type); echo "You can only Upload the following types of files: ",$text,"
"; }

The following is to rename them,

<ol class="dp-xml">
<li class="alt"><span><span>else { </span></span></li>
<li class="alt"><span><span>$</span><span class="attribute">filename</span><span>=</span><span class="attribute-value">explode</span><span>(".",$_FILES['userfile']['name']);</span></span></li>
<li class="alt"><span><span>//把上传的文件名以“.”好为准做一个数组。 </span></span></li>
<li class="alt"><span><span>$</span><span class="attribute">time</span><span>=</span><span class="attribute-value">date</span><span>("m-d-H-i-s");</span></span></li>
<li class="alt"><span><span>//去当前上传的时间 $filename[0]=$time;</span></span></li>
<li class="alt"><span><span>//取文件名t替换 </span></span></li>
<li class="alt"><span><span class="attribute">name</span><span>=</span><span class="attribute-value">implode</span><span>(".",$filename); </span></span></li>
<li class="alt"><span><span>//上传后的文件名 </span></span></li>
<li class="alt"><span><span>$</span><span class="attribute">uploadfile</span><span>=$uploaddir.$name;</span></span></li>
<li class="alt"><span><span>//上传后的文件名地址 }  </span></span></li>
</ol>

PHP upload pictures 3. Finally Upload the file to the specified directory. After successful upload, the function used to output the preview of the uploaded image

<ol class="dp-xml">
<li class="alt"><span><span>{ move_uploaded_file：执行上传文件 } </span></span></li>
<li class="alt"><span><span>if(move_uploaded_file</span></span></li>
<li class="alt">
<span><span>(</span></span><span><span>$_FILES['userfile']['tmp_name'],$uploadfile)) </span></span>
</li>
<li class="alt"><span><span>{ echo "</span></span></li>
<li class="alt"><span><span class="tag"><span class="tag-name">center</span><span class="tag">></span><span>您的文件已经上传完毕 上传图片预览:</span></span></span></li>
<li class="alt"><span><span> center</span><span class="tag">></span><span class="tag"><span class="tag-name">br</span><span class="tag">></span></span></span></li>
<li class="alt"><span><span class="tag"><span class="tag-name">center</span><span class="tag">></span><span class="tag"><span class="tag-name">img</span><span> </span><span class="attribute">src</span><span>=</span><span class="attribute-value">'$uploadfile'</span><span class="tag">></span><span>center</span><span class="tag">></span><span>";</span></span></span></span></li>
<li class="alt"><span><span> echo"</span><span class="tag"><span class="tag-name">br</span><span class="tag">></span><span class="tag"><span class="tag-name">center</span><span class="tag">></span></span></span></span></li>
<li class="alt"><span><span class="tag"><span class="tag-name">a</span><span> </span><span class="attribute">href</span><span>=</span><span class="attribute-value">'javascrīpt:history.go(-1)'</span><span class="tag">></span></span></span></li>
<li class="alt"><span><span>继续上传a</span><span class="tag">></span><span>center</span><span class="tag">></span><span>"; } </span></span></li>
<li class="alt"><span><span>else { echo"传输失败！"; } </span></span></li>
</ol>

The above is an introduction to the relevant methods of uploading images in PHP. I hope it will be helpful to everyone.

http://www.bkjia.com/PHPjc/446236.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/446236.htmlTechArticleWhen we upload images in actual operation, the principle is: first determine whether the file type is an image format, if so, upload the file, and then Rename files (usually to avoid uploading files with duplicate names, now...