Decrease the maximum number of connections to your web server. 20 is probably a realistic number. For Apache, this is MaxClients.
Do not, without a good reason, have more than one connection to MySQL from each PHP script.
Your screen shot shows only 111 as "max concurrent conections". (Presumably this comes from
SHOW GLOBAL STATUS LIKE 'Max_used_connections';) So,
max_connections is much too high. I rarely see a need for more than 1000. In your case, there is evidence that 111 is high enough.
Since it is dangerous (for RAM usage) to set
max_connections too high, I suggest you decrease it to 200.
"Failed attempts" sounds a bit like the
Aborted_connects. For that, 453/hour is moderately high, but I don't see it as a red flag. It could be that some hacker has tried to get in. Is port 3306 exposed outside your machine/LAN?
If you would like further analysis, please provide
SHOW GLOBAL STATUS; and
SHOW VARIABLES;, plus how much RAM. (Probably need a postit-like site.)