What should you pay attention to when troubleshooting NOTICE in php?

The call seems to have been successful...but I really don’t know what the problem is with this notice

---

Modified as follows...function update($link, $data, $table, $where = null) {

<code>foreach ( $data as $key => $val ) {
    $set .= "{$key}='{$val}',";
}
$set = trim ( $set, ',' );
$where = $where == null ? '' : ' WHERE ' . $where;
$query = "UPDATE {$table} SET {$set} {$where}";
$res = mysqli_query ( $link, $query );
if ($res) {
    return mysqli_affected_rows ( $link );
} else {
    return false;
}</code>

}

·······

I have also defined this set... There will still be problems = =

Reply content:

The call seems to have been successful...but I really don’t know what the problem is with this notice

---

Modified as follows...function update($link, $data, $table, $where = null) {

<code>foreach ( $data as $key => $val ) {
    $set .= "{$key}='{$val}',";
}
$set = trim ( $set, ',' );
$where = $where == null ? '' : ' WHERE ' . $where;
$query = "UPDATE {$table} SET {$set} {$where}";
$res = mysqli_query ( $link, $query );
if ($res) {
    return mysqli_affected_rows ( $link );
} else {
    return false;
}</code>

}

·······

I have also defined this set... There will still be problems = =

You did not define the set variable in the function scope. The reason for reporting the notice is that this is not a fatal error. It just reminds you that using undefined variables may bring adverse consequences.

After reading your revised question, set is still not defined. To be defined before using it. .= is equivalent to using it, and it must be within the function scope, not the foreach scope.

The $set variable is not defined and needs to be defined first above foreach:

<code>$set = '';</code>

The number of rows displayed in general error reports, you can find the problem from the row above the row number

First define a variable $set

Undefined variableUndefined variable

$set must be defined first. If it is not defined, use ‘.=’ directly. This is wrong usage

1. Use error_reporting(0)or modify error_reporting = E_ALL & ~E_NOTICE in php.ini

2. Variable initialization $set = '';foreach($data as $k=>$v){$set.="{$k}={$v},";}

Define $set = '';

before foreach