Detailed analysis of three steps to upload images in PHP_PHP tutorial

When learning PHP, you may encounter the problem of uploading images in PHP. Here we will introduce the solution to the problem of uploading images in PHP and share it with you here. Today we will start learning PHP to upload images together. Principle of uploading images: first determine whether the file type is an image format, if so, upload the file, then rename the file (usually to avoid uploading files with duplicate names, now they are basically named after time), and then upload the file to the specified directory , output a preview of the uploaded image after successful upload.

1. First we start with the function used to determine whether the file type is an image type

<ol class="dp-xml">
<li class="alt"><span><span>{  </span></span></li>
<li class=""><span>strrchr:查找字符串在另一个字符串中最后一次出现的位置，并返回从该位置到字符串结尾的所有字符。  </span></li>
<li class="alt"><span>substr: 取部份字符串。  </span></li>
<li class=""><span>$HTTP_POST_FILES['file']['name']:获取当前上传的文件全称。  </span></li>
<li class="alt"><span>} </span></li>
</ol>

The image type is the character after "." (for example: 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

<ol class="dp-xml"><li class="alt"><span><span class="tag"><strong><font color="#006699"><?</FONT></STRONG></SPAN><SPAN> </SPAN></SPAN><LI class=""><SPAN></SPAN><SPAN class=tag-name><STRONG><FONT color=#006699>function</FONT></STRONG></SPAN><SPAN> type()  </SPAN></SPAN><LI class=alt><SPAN>{  </SPAN><LI class=""><SPAN>return substr(strrchr($HTTP_POST_FILES['file']['name'],'.'),1);  </SPAN><LI class=alt><SPAN>}  </SPAN><LI class=""><SPAN></SPAN><SPAN class=tag><STRONG><FONT color=#006699>?></font></strong></span><span> </span></span></li></ol>

2. If so, upload the file, and then rename the file’s function

<ol class="dp-xml">
<li class="alt"><span><span>{  </span></span></li>
<li class=""><span>strtolower:把字符串的字母全部转换为小写字母.  </span></li>
<li class="alt"><span>in_array： 函数在数组中搜索给定的值。  </span></li>
<li class=""><span>implode：函数把数组元素组合为一个字符串  </span></li>
<li class="alt"><span>random:随机生成的数  </span></li>
<li class=""><span>$_FILES['userfile']['name']:上传文件名称  </span></li>
<li class="alt">
<span>$uploaddir：自己定义的变量。比如在同一个文件夹里面，你想把上传的文件放到这个文件夹的FILE文件夹下，你可以这样定义$</span><span class="attribute"><font color="#ff0000">uploaddir</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">"./file/"</font></span><span>；注意写法  </span>
</li>
<li class=""><span>} </span></li>
</ol>

There will be many problems here. First, write an array that can upload 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.

<ol class="dp-xml">
<li class="alt"><span><span>if(!in_arry(strtolower(type()),$type))//如果不存在能上传的类型  </span></span></li>
<li class=""><span>{  </span></li>
<li class="alt">
<span>$</span><span class="attribute"><font color="#ff0000">text</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">implode</font></span><span>('.',$type);  </span>
</li>
<li class="">
<span>echo "您只能上传以下类型文件: ",$text,"</span><strong><font color="#006699"><span class="tag"><</SPAN><SPAN class=tag-name>br</SPAN><SPAN class=tag>></span></font></strong><span>";  </span>
</li>
<li class="alt"><span>} </span></li>
</ol>

The following is to rename them,

<ol class="dp-xml">
<li class="alt"><span><span>else  </span></span></li>
<li class=""><span>{  </span></li>
<li class="alt">
<span>$</span><span class="attribute"><font color="#ff0000">filename</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">explode</font></span><span>(".",$_FILES['userfile']['name']);//把上传的文件名以“.”好为准做一个数组。  </span>
</li>
<li class="">
<span>$</span><span class="attribute"><font color="#ff0000">time</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">date</font></span><span>("m-d-H-i-s");//去当前上传的时间  </span>
</li>
<li class="alt"><span>$filename[0]=$time;//取文件名t替换  </span></li>
<li class="">
<span></span><span class="attribute"><font color="#ff0000">name</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">implode</font></span><span>(".",$filename); //上传后的文件名  </span>
</li>
<li class="alt">
<span>$</span><span class="attribute"><font color="#ff0000">uploadfile</font></span><span>=$uploaddir.$name;//上传后的文件名地址  </span>
</li>
<li class=""><span>} </span></li>
</ol>

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

<ol class="dp-xml">
<li class="alt"><span><span>{  </span></span></li>
<li class=""><span>move_uploaded_file：执行上传文件  </span></li>
<li class="alt"><span>}  </span></li>
<li class=""><span>if(move_uploaded_file($_FILES['userfile']['tmp_name'],$uploadfile))  </span></li>
<li class="alt"><span>{  </span></li>
<li class="">
<span>echo "</span><strong><font color="#006699"><span class="tag"><</SPAN><SPAN class=tag-name>center</SPAN><SPAN class=tag>></span></font></strong><span>您的文件已经上传完毕 上传图片预览: </span><strong><font color="#006699"><span class="tag"></</SPAN><SPAN class=tag-name>center</SPAN><SPAN class=tag>></span><span class="tag"><</SPAN><SPAN class=tag-name>br</SPAN><SPAN class=tag>></span><span class="tag"><</SPAN><SPAN class=tag-name>center</SPAN><SPAN class=tag>></span><span class="tag"><</SPAN><SPAN class=tag-name>img</SPAN></FONT></STRONG><SPAN> </SPAN><SPAN class=attribute><FONT color=#ff0000>src</FONT></SPAN><SPAN>=</SPAN><SPAN class=attribute-value><FONT color=#0000ff>'$uploadfile'</FONT></SPAN><STRONG><FONT color=#006699><SPAN class=tag>></span><span class="tag"></</SPAN><SPAN class=tag-name>center</SPAN><SPAN class=tag>></span></font></strong><span>";  </span>
</li>
<li class="alt">
<span>echo"</span><strong><font color="#006699"><span class="tag"><</SPAN><SPAN class=tag-name>br</SPAN><SPAN class=tag>></span><span class="tag"><</SPAN><SPAN class=tag-name>center</SPAN><SPAN class=tag>></span><span class="tag"><</SPAN><SPAN class=tag-name>a</SPAN></FONT></STRONG><SPAN> </SPAN><SPAN class=attribute><FONT color=#ff0000>href</FONT></SPAN><SPAN>=</SPAN><SPAN class=attribute-value><FONT color=#0000ff>'javascrīpt:history.go(-1)'</FONT></SPAN><SPAN class=tag><STRONG><FONT color=#006699>></span></font></strong><span>继续上传</span><strong><font color="#006699"><span class="tag"></</SPAN><SPAN class=tag-name>a</SPAN><SPAN class=tag>></span><span class="tag"></</SPAN><SPAN class=tag-name>center</SPAN><SPAN class=tag>></span></font></strong><span>";  </span>
</li>
<li class=""><span>}  </span></li>
<li class="alt"><span>else  </span></li>
<li class=""><span>{  </span></li>
<li class="alt"><span>echo"传输失败！";  </span></li>
<li class=""><span>} </span></li>
</ol>

That’s it. A simple program for uploading pictures has been written. If you still want to improve your functions, you can add them yourself!

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