How to implement conditional query in php

How to implement conditional query in php: first call the previously encapsulated class; then use keyword fuzzy query; then create a form, submit the data to the current page, extract the keyword query; and finally use PHP code Traverse the elements in the table and turn the keywords into red.

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1. Single condition Query is a query with only one condition:

1. First call the previously encapsulated class, and then use keywords to fuzzy query:

<?php //单查询
require "DBDA.class.php";//调取封装类
$db=new DBDA;
$Sname="";//创建变量，为了后面可以让Sname在表单中显示
$sql="select * from t_student";

if(!empty($_POST["Sname"]))//确定是否存在数据
{
    $Sname=$_POST["Sname"];
    $sql="select * from t_student where Sname like &#39;%{$Sname}%&#39; ";//模糊查询
}
?>

2. Create a form, submit the data to the current page, and extract the keyword query:

<form action="chaxun.php" method="post"><!--因为查询数据在当前页面，所以提交到当前页面-->
<div>姓名：<input type="text" name="Sname" value="<?php echo $Sname ?>" />
<input type="submit" value="查询" /></div>
</form><br />

<table width="100% " border="1" cellpadding="0" cellspacing="0">
    <tr>
        <td>姓名</td>
        <td>性别</td>
        <td>班级</td>
    </tr>

3. Traverse the elements in the table and turn the keywords into red:

<?php
$arr=$db->query($sql);
foreach($arr as $v)
{
    $str = str_replace($Sname,"<span style=&#39;color:red&#39;>{$Sname}</span>",$v[1]);//用span标签使关键字变为红色，
    echo "<tr>
        <td>{$str}</td>
        <td>{$v[2]}</td>
        <td>{$v[4]}</td>
        </tr>";    
}
?>

Final result:

## 2. Multi-condition query:

1. First make a form and create a table to display the table:

<table width="100%" border="1" cellpadding="0" cellspacing="0">
<tr>
    <td>代号</td>
    <td>名称</td>
    <td>系列</td>
    <td>上市时间</td>
    <td>价格</td>
</tr>
</table>

2. Call the encapsulation class, create corresponding conditions, and check whether the data is empty :

<?php
require "DBDA.class.php";
$db=new DBDA();//1.如果没有提交数据，显示所有//2.如果有提交数据，根据关键字查询显示$name="";
$tj1=" 1=1 "; //第一个条件，对应名称，要用空格隔开$tj2=" 1=1 ";//第二个条件，对应系列，要用空格隔开if(!empty($_POST["name"]))
{
    $name = $_POST["name"];
    $tj1 = " name like &#39;%{$name}%&#39; ";
}if(!empty($_POST["brand"]))
{
    $brand = $_POST["brand"];
    $tj2 = " brand = &#39;{$brand}&#39; ";
}//总条件$tj=" {$tj1}and{$tj2} ";
$sql="select * from car where".$tj;?>

3. Use PHP code to traverse the database table and turn the keywords into red (php should be embedded in the table):

<?php
$arr = $db->query($sql);foreach($arr as $v)
{
    $str = str_replace($name,"<span style=&#39;color:red&#39;>{$name}</span>",$v[1]);
    echo "<tr>
    <td>{$v[0]}</td>
    <td>{$str}</td>
    <td>{$v[2]}</td>
    <td>{$v[3]}</td>
    <td>{$v[7]}</td>
</tr>";}?>

The final result is:

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