Commonly used php functions_PHP tutorial
File reading function
//File reading function
function PHP_Read($file_name) {
$fd=fopen($file_name,r);
while($bufline=fgets($fd, 4096)){
$buf.=$bufline;
}
fclose($fd);
Return $buf;
}
?>
File writing function
//File writing function
function PHP_Write($file_name,$data,$method="w") {
$filenum=@fopen($file_name,$method);
flock($filenum,LOCK_EX);
$file_data=fwrite($filenum,$data);
fclose($filenum);
Return $file_data;
}
?>
Static page generation function
//Static page generation function
function phptohtm($filefrom,$fileto,$u2u=1){
if($u2u==1){
$data=PHP_Read($filefrom);
}else{
$data=$filefrom;
}
PHP_Write($fileto,$data);
Return true;
}
?>
Specify condition information quantity retrieval function
//Specify condition information quantity retrieval function
function rec_exist($table,$where){
$query="select count(*) as num from $table ".$where;
$result=mysql_query($query) or die(nerror(1));
$rowcount=mysql_fetch_array($result);
$num=$rowcount["num"];
if ($num==0){
Return false;
}
Return $num;
}
?>
Directory deletion function
//Directory deletion function
function del_DIR($directory){
$mydir=dir($directory);
while($file=$mydir->read()){
if((is_dir("$directory/$file")) AND ($file!=".") AND ($file!="..")){
del_DIR("$directory/$file");
}else{
if(($file!=".") AND ($file!="..")){
unlink("$directory/$file");
//echo "unlink $directory/$file ok
";
}
}
}
$mydir->close();
rmdir($directory);
//echo "rmdir $directory ok
";
}
?>
Directory name validity detection function
//Directory name legality detection
function isen($str){
$ret="";
for($i=0;$i $p=ord(substr($str,$i,1));
if(($p57 & $p90 & $p122){
nerror("Does not meet the specification!");
}
$ret.=chr($p);
}
Return $ret;
}
?>
Pagination function
//Paging function
function splitlist($HALT,$LRLIST,$ECHOCNT,$paper,$table,$where,$page_id,$userid){
global $splitstr,$sumcnt;
if($paper=="" || $sumcnt==""){
$query = "select count(*) as num from $table $where";
$result = mysql_query($query);
$row = mysql_fetch_array($result);
$sumcnt=$row["num"];
if($sumcnt==0){
nerror("There is no choice to publish news in this version!");
}
$paper=1;
}
$sumpaper=($sumcnt-$sumcnt%$ECHOCNT)/$ECHOCNT;
if(($sumcnt%$ECHOCNT)!=0) $sumpaper+=1;
if($sumpaper==1 && $HALT==0) return($where);
$enwhere=base64_encode(base64_encode($where));
if(($LRLIST*2+1)
if(($paper-$LRLIST)
$tract=1;
$sub=$LRLIST*2+1;
}else if(($paper+$LRLIST) >= $sumpaper){
$tract=$sumpaper-($LRLIST*2);
$sub=$sumpaper;
}else{
$tract=$paper-$LRLIST;
$sub=$paper+$LRLIST;
}
}else{
$tract=1;
$sub=$sumpaper;
}
$uppaper=$paper-1;
$downpaper=$paper+1;
$startcnt=($paper-1)*$ECHOCNT;
$where.=" limit ${ startcnt },${ ECHOCNT }";
if($tract > 1) { $splitstr="【
else $splitstr="【
for($i=$tract;$i
if ($i!=$paper) $splitstr.="".$i." ";
else $splitstr.="".$i." ";
}
if ($sub!=$sumpaper) $splitstr.=">> 】";
else $splitstr.=">> 】";
return($where);
}
?>
Instructions for using paging functions
/*
#### Retrieve paging function ####
Int $HALT - Whether (1/0) displays the page number bar when the search results are only divided into 1 page
Int $LRLIST - (The page number bar displays the page number-1)/2
Int $ECHOCNT - The number of records displayed on each page during retrieval
Int $paper - number of pages, prefetch: $paper=$HTTP_GET_VARS[paper];
Varchar $table - data table name, pre-attached value: $table="db.table";
Varchar $where - search conditions, pre-attached value: $where="where field='value'";
Varchar $enwhere - Encode the original $where twice with base64_encode() and submit it in the form of GET
Varchar $splitstr - page number bar output string, execute the function at the corresponding position echo $splitstr;
Variables need to be obtained before function call -
$paper=$HTTP_GET_VARS[paper];
$sumcnt=$HTTP_GET_VARS[sumcnt];
$enwhere=$HTTP_GET_VARS[enwhere];
Return (Varchar $where) - Search conditions for search statements after paging
Note: This function needs to call the error handling function nerror($error);
*/
?>
Image file upload function
//Image file upload function
function upload_img($UploadFile,$UploadFile_name,$UploadFile_size,$UploadPath,$max_size=64){
//$TimeLimit=60; //Set the timeout limit time. The default time is 30 seconds. When set to 0, there is no time limit
//set_time_limit($TimeLimit);
if(($UploadFile!= "none" )&&($UploadFile != "" )){
$FileName=$UploadPath.$UploadFile_name;
if($UploadFile_size
$FileSize="(string)$UploadFile_size" . "Bytes";
}elseif($UploadFile_size
$FileSize=number_format((double)($UploadFile_size / 1024), 1) . " KB";
}else{
nerror("File exceeds limit size!");
}
//{
//$FileSize="number_format((double)($UploadFile_size" / (1024 * 1024)), 1) . " MB";
// }
if(!file_exists($FileName)){
if(copy($UploadFile,$FileName)){
Return "$UploadFile_name ($FileSize)";
}else{
nerror("File $UploadFile_name upload failed!");
}
unlink($UploadFile);
}else{
nerror("The file $UploadFile_name already exists!");
}
//set_time_limit(30); //Restore the default timeout setting
}
}
?>

In PHP, you can use session_status() or session_id() to check whether the session has started. 1) Use the session_status() function. If PHP_SESSION_ACTIVE is returned, the session has been started. 2) Use the session_id() function, if a non-empty string is returned, the session has been started. Both methods can effectively check the session state, and choosing which method to use depends on the PHP version and personal preferences.

Sessionsarevitalinwebapplications,especiallyfore-commerceplatforms.Theymaintainuserdataacrossrequests,crucialforshoppingcarts,authentication,andpersonalization.InFlask,sessionscanbeimplementedusingsimplecodetomanageuserloginsanddatapersistence.

Managing concurrent session access in PHP can be done by the following methods: 1. Use the database to store session data, 2. Use Redis or Memcached, 3. Implement a session locking strategy. These methods help ensure data consistency and improve concurrency performance.

PHPsessionshaveseverallimitations:1)Storageconstraintscanleadtoperformanceissues;2)Securityvulnerabilitieslikesessionfixationattacksexist;3)Scalabilityischallengingduetoserver-specificstorage;4)Sessionexpirationmanagementcanbeproblematic;5)Datapersis

Load balancing affects session management, but can be resolved with session replication, session stickiness, and centralized session storage. 1. Session Replication Copy session data between servers. 2. Session stickiness directs user requests to the same server. 3. Centralized session storage uses independent servers such as Redis to store session data to ensure data sharing.

Sessionlockingisatechniqueusedtoensureauser'ssessionremainsexclusivetooneuseratatime.Itiscrucialforpreventingdatacorruptionandsecuritybreachesinmulti-userapplications.Sessionlockingisimplementedusingserver-sidelockingmechanisms,suchasReentrantLockinJ

Alternatives to PHP sessions include Cookies, Token-based Authentication, Database-based Sessions, and Redis/Memcached. 1.Cookies manage sessions by storing data on the client, which is simple but low in security. 2.Token-based Authentication uses tokens to verify users, which is highly secure but requires additional logic. 3.Database-basedSessions stores data in the database, which has good scalability but may affect performance. 4. Redis/Memcached uses distributed cache to improve performance and scalability, but requires additional matching

Sessionhijacking refers to an attacker impersonating a user by obtaining the user's sessionID. Prevention methods include: 1) encrypting communication using HTTPS; 2) verifying the source of the sessionID; 3) using a secure sessionID generation algorithm; 4) regularly updating the sessionID.


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